Matt Mullenweg started WordPress, which now powers 16 percent of the web. Mullenweg dropped out of the University of Houston in 2004. Even then, he was so precocious that he didn't bother with their computer classes. For the Chronicle: Thomas B. Shea

Daniel Ek co-founded the wildly popular music streaming service Spotify at age 21. Ek left his studies in engineering at the Royal Institute of Technology in Sweden after eight weeks in 2005, but became a millionaire just a few years later. Photo: Iabuk, Flickr

Aaron Levie started enterprise software company Box, and the company could IPO at a $3 billion valuation. Levie dropped out of USC after coming up with the idea that became Box.net, a cloud content management system. He got $350,000 in funding from Mark Cuban.

Jack Dorsey brought Twitter from a small side project to a global social network and founded payments startup Square. Dorsey moved to New York to study at NYU because he was fascinated by taxi dispatch systems, but dropped out in 1999. That fascination, combined with his experience using LiveJournal, formed the idea for Twitter.

Before founding a million-dollar company, Threadless co-founder Jeffrey Kalmikoff was kicked out of one school and dropped out of another. Kalmikoff dropped out of graphic design school in Chicago in the late '90s. He helped build t-shirt company Threadless from a side project into a million-dollar company as a co-founder and chief creative officer. Photo: Turoczy, Flickr

Zach Sims started Codeacademy, which has over a million users and raised more than $10 million from investors last year, including Richard Branson. Sims dropped out of Columbia in 2011 to build Codeacademy. Photo: LeWeb12, Flickr

Zach Sims Zach Sims started Codeacademy, which has over a... Photo-4314865.58279 - SFGate

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Kevin Rose

Kevin Rose founded Digg in 2004, which was nearly bought by Google for $200 million. He’s now a partner at Google Ventures. Rose dropped out of the University of Nevada Las Vegas in 1998. He wrote his first software program in the second grade and launched Digg with $1,200.

Shawn Fanning founded Napster and made the cover of Time at the age of 19. In 1999, Fanning decided to leave Northeastern University to move to Silicon Valley and further develop Napster. His net worth is estimated at $7.5 million.

Shawn Fanning Shawn Fanning founded Napster and made the cover... Photo-4314861.58279 - SFGate

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Taboola Gallery Frame Item-85307.58279 - SFGate

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Evan Williams

Evan Williams started Blogger, a massive blogging platform and one of Google's early acquisitions, and later he became Twitter's CEO. Williams made it through just a year and a half at the University of Nebraska before realizing it wasn't for him in 1991.

David Karp created Tumblr, now the 9th-most visited site in the United States, despite never graduating high school. Karp was already a product manager at UrbanBaby, an internet forum for parents, at the age of 16. He had dropped out of Bronx Science high school a year earlier in 2001 to be home schooled, and never obtained a high school diploma. Photo by Ben Gabbe/Getty Images for Mercedes-Benz Fashion Week

David Karp David Karp created Tumblr, now the 9th-most visited... Photo-4314858.58279 - SFGate

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Ben Milne

Ben Milne turned his payment platform from a $1,200 investment to a multi-million-dollar company by the age of 22. A decade ago, twenty-eight-year-old Ben Milne dropped out of the University of Northern Iowa to start his first company, Elemental Designs. In 2008, he moved on to Dwolla, an online payment system that allows you to eliminate credit cards completely.

Jeri Ellsworth dropped out of high school, then dropped out of college and still managed to create a product that landed in The NYT. She created a Commodore 64 emulator that allowed her to play 30 video games from a single joystick. Photo: Jeri Ellsworth, Flickr

Stacey Ferreira dropped out of NYU when she received news that Virgin Mogul Richard Branson and Jerry Murdock would be investing in her cloud-based startup, MySocialCloud.com. (Photo: TEDxYouth@SanDiego, Flickr)